1. Technical Field to Which the Invention Belongs
The present invention relates to a method of and a structure for connecting an electric wire and a connecting terminal in which core wire portions of an electric wire are caulked by caulking portions of a connecting terminal so establish electrical connection.
2. Related Art
Various crimp terminals are known in which a conductor portion of an electric wire is caulked by caulking portions of a connecting terminal so establish electrical connection.
As shown in FIG. 11, a tip portion of a sheath portion S of a sheathed wire W is stripped by a predetermined length, and core wire portions M are exposed in an axially extended state. In addition, a connecting terminal 51 is formed by stamping a metal plate. The connecting terminal 51 has in its rear portion a sheath caulking portion 52, a conductor caulking portion 53 and a positioning portion 54 with a pair of positioning grooves 55. The connecting terminal 51 has in its front portion a pin-shaped contact portion 56 which electrically contacts a mating female terminal.
To connect the sheathed wire W to the connecting terminal 51, after the sheath portion S of the sheathed wire W is placed on the sheath caulking portion 52, and the core wire portions M are placed on the conductor caulking portion 53, both caulking portions 52 and 53 are caulked by an unillustrated automatic terminal crimping apparatus, as shown in FIG. 12. As for the conductor caulking portion 53 in this state, the core wire portions M are merely caulked by the conductor caulking portion 53 as shown in FIG. 13, the mutual contact is mere contact at a plurality of points, so that there has been a problem in that heat is generated if a large current flows.
Accordingly, it is the general practice to solder the caulked conductor caulking portion 53 and the core wire portions M. Consequently, since the solder is present between the core wire portions M and the conductor caulking portion 53, the area of electrical contact becomes large, and heat is made difficult to generate, so that a highly reliable connecting structure can be obtained.
In addition, since it is possible to prevent the formation of oxide films on the core wire portions M and the inner surface of the conductor caulking portion 53, it is possible to maintain stable conductivity.
However, with the above-described general structure for connecting an electric wire and a connecting terminal, since flux for solder is necessarily used for soldering. There has been a problem in that the core wire portions of the wire become corroded.
In addition, since the soldering operation is difficult to be incorporated into a continuous automation line in the process for caulking connecting terminals. There is a problem in that productivity is lowered.
The invention has been devised in view of the above-described problems, and its object is to provide a method of and a structure for connecting an electric wire and a connecting terminal which are capable of maintaining excellent conductivity without corrosion and of coping with a continuous automation line as well.
The above problems concerning the invention can be overcome by a method of connecting an electric wire and a connecting terminal, said electric wire having a core wire portion and a sheath, said core wire portion exposed from an end of said sheath, said connecting terminal having a conductor caulking portion to caulk said core wire portion, said method including the steps of:
applying a metal member to said core wire portion, a ductility of said metal member being higher than that of said core wire portion;
caulking said core wire portion by said conductor caulking portion to contact an inner surface of said conductor caulking portion with said metal member together; and
fusing said metal member.
In accordance with the method of connecting an electric wire and a connecting terminal constructed as described above, if the conductor caulking portion of the connecting terminal is caulked onto the wire via a ductile metal, the ductile metal is deformed by the contact portion and enters gaps between adjacent ones of the core wire portions and between the core wire portions and the connecting terminal. Subsequently, by heating and fusing the metal, adjacent ones of the core wire portions as well as the core wire portions and the connecting terminal are joined. Consequently, the area of contact between the core wire portions and the connecting terminal increases, and the formation of oxide films is prevented, so that it is possible to maintain excellent conductivity, thereby making it possible to ensure high reliability. In addition, since soldering is not performed, it is possible to prevent corrosion attributable to flux and easily incorporate the connecting method of the invention into a continuous automation line, thereby making it possible to enhance productivity.
In addition, the above problems concerning the invention can be overcome by a method of connecting an electric wire and a connecting terminal, said electric wire having a core wire portion and a sheathed wire, said core wire portion exposed from an end of said sheathed wire, said connecting terminal having a conductor caulking portion to caulk said core wire portion, said method including the step of:
caulking said core wire portion by said conductor caulking portion to contact of an inner surface of said conductor caulking portion with said core wire portion;
applying a liquefied resin between said inner surface and said core wire portion; and
curing said liquefied resin.
In addition, as the liquefied resin, it is possible to cite a phenolic resin, an instantaneous adhesive agent, or the like, but the liquefied resin is not particularly limited.
The above problems concerning the invention can be overcome by a structure for connecting an electric wire and a connecting terminal including:
said electric wire having a core wire portion and a sheathed wire, said core wire portion defined by exposing an end of said sheathed wire, said connecting terminal having a conductor caulking portion to caulk said core wire portion, said core wire portion extending to an axial direction from said an end portion of said sheathed wire; and
a metal member provided between said core wire portion and an inner surface of said conductive caulking portion, a ductility of said metal member being higher than that of said core wire portion.
In accordance with the structure for connecting an electric wire and a connecting terminal constructed as described above, since the conductor caulking portion of the connecting terminal is caulked onto the core wire portions of the wire via a tubular member or a tape-like member formed of a ductile metal, the ductile metal is deformed by the contact portion and enters the gaps between adjacent ones of the core wire portions and between the core wire portions and the connecting terminal. subsequently, by heating and fusing this tubular member or tape-like member, the core wire portions and the conductor caulking portion of the connecting terminal are joined. Consequently, the area of contact between the core wire portions and the connecting terminal increases, and the formation of oxide films attributable to flux is prevented, so that it is possible to maintain excellent conductivity, thereby making it possible to ensure high reliability.
In addition, since the ductile metal is a tubular member or tape-like member, a general connecting terminal can be used as it is, and the incorporation into a continuous automation line is facilitated. Accordingly, it is possible to easily improve the conductivity of general connecting terminals and to easily enhance the reliability of the connecting terminals, and it is possible to improve productivity.
In addition, the tubular member or the tape-like member is fused by any one of a spot heater, a soldering iron, ultrasonic welding, and a laser.
The above problems concerning the invention can be overcome by a structure for connecting an electric wire and a connecting terminal comprising:
said electric wire having a core wire portion and a sheath, said core wire portion exposed from an end of said sheath, said core wire portion extending in an axial direction from said end of said sheath;
said connecting terminal having a conductor caulking portion to caulk said core wire portion;
a metal film formed at an inner surface of said conductor caulking portion, a ductility of said metal film being higher than that of said core wire portion;
wherein said core wire portion is caulked by said conductor caulking portion to contact said metal film with aid metal member.
In accordance with the structure for connecting an electric wire and a connecting terminal constructed as described above, if the conductor caulking portion of the connecting terminal is caulked onto the wire via a metal whose ductility is higher than that of the core wire portions, the ductile metal is deformed by the contact portion and enters the gaps between adjacent ones of the core wire portions or between the core wire portions and the connecting terminal. Consequently, the area of contact between the core wire portions and the connecting terminal increases, and the formation of oxide films is prevented, so that it is possible to maintain excellent conductivity, thereby making it possible to ensure high reliability. In addition, since it is possible to immediately proceed to the caulking operation, productivity can be improved.
In addition, in the above-described structure for connecting an electric wire and a connecting terminal, the metal film is preferably formed on the inner surface of the conductor caulking portion by plating or vacuum deposition. Further, in the above-described structure for connecting an electric wire and a connecting terminal, the metal film is preferably formed by causing a ductile film to adhere to the inner surface of the conductor caulking portion by plating.
In accordance with the structure for connecting an electric wire and a connecting terminal constructed as described above, since the ductile metal is formed on the inner surface of the conductor caulking portion by plating, vacuum deposition, or adhesion, it is possible to immediately proceed to the caulking operation, thereby making it possible to improve productivity further.
The aforementioned ductility if a kind of plasticity including ductility or malleability, and refers to a property in which a metal is drawn without being fractured or is spread in the form of a foil by a stress exceeding a limit of elasticity, such as pressure and impact.
In addition, the aforementioned ductile metal is, for instance, gold, silver, lead, zinc, aluminum or the like, and is a soft metal whose ductility is higher than that of at least the caulking portion of the connecting terminal.
In addition, the ductile metal in terms of its form is preferably a tubular ring or a tape-like film which is separate from the connecting terminal, or a metal film formed on the inner surface of the conductor caulking portion of the connecting terminal, but the form of the ductile metal is not particularly limited.